This invention is directed to a fabric or material suitable for use as a cover material or bodyside liner for a personal care absorbent article having improved fluid handling properties.
Almost all personal care absorbent articles include a cover material or a bodyside liner, an absorbent structure or core underlying the cover material, and some type of backing material which is generally liquid impervious to help prevent leakage. The types of cover materials generally fall into two main groups based, at least in part, upon performance and aesthetic preferences. For example, in the area of feminine care and sanitary napkins, the market is polarized into two segments, women who prefer clean and dry film covers and women who prefer soft, cloth-like nonwoven covers. The advantage of film covers for sanitary napkins is that they provide a relatively clean and dry surface as menses tends to pass through the film layer and into the interior of the absorbent product. A drawback, however, is that such film layers do not provide the degree of softness and comfort that a nonwoven cover material can provide. An additional drawback is the smooth, slick, non-clothlike feel that is characteristic of many films. Nonwoven-based cover materials, on the other hand, are very soft and cloth-like in feel, but tend to retain more of the menses at or just below the surface of the cover material which, in turn, makes the product suffer from the standpoint of properties such as cleanliness and dryness. The difference in functionality is a direct result of the structure of nonwovens including small average pore size and nonuniform pore size distribution.
Conventional hydrophilic cover materials or bodyside liners in contact with the skin effectively transport body fluids into the absorbent core, but they cause a wet feel against the skin of the user and may adversely affect skin health. In addition, they may wick liquid in the plane of the layer, allowing liquid to approach the edges of the absorbent article and possibly leak or seep out.
To achieve the goal of softness and a dry feel in topsheets of absorbent articles, many manufacturers have turned to nonwoven fabrics made of hydrophobic fibers for the body-contacting topsheet. While the use of hydrophobic nonwoven fabrics results in improved dry feel, the hydrophobic material hinders wicking into the absorbent core causing fluid to pool on the surface until enough pressure is applied to permeate the structure under conditions of low pressure and flow. As a result, the fluid may run off the pad and leak.
To improve the poor wicking and absorbent properties of hydrophobic materials, it is known to apply a finish comprising surfactants on the surface of the hydrophobic fibers, rendering them wettable or introducing fibers which are intrinsically wettable. Intrinsically wettable fibers may be natural, such as cellulose, or synthetic, such as rayon, polyester, or polyamides. Although providing good intake properties, wettable fibers introduce higher fluid retention and more fluid staining.
In the case of absorbent pads for feminine care, two distinct approaches involving topsheets or covers are commonly employed. One approach is to use a soft, clothlike nonwoven hydrophilic material which increases comfort but has the drawback of fluid retention and staining. A second approach is to use an apertured plastic film of hydrophobic polymer or other materials. The hydrophobic cover material repels many body fluids while the apertures allow wicking away from the cover into the absorbent material below.
Accordingly, there is a need for an improved cover material which can provide the clean and dry feel characteristic of hydrophobic film cover materials while also delivering the softness of nonwoven cover materials.
The present invention is directed to a fabric or material suitable for use as a cover material or bodyside liner for a personal care absorbent article. The material exhibits a unique topography and texture that enhances the material""s visual and tactile properties and also increases its permeability. When used as a cover material or bodyside liner in a personal care absorbent article, the material has superior fluid handling characteristics. Further, the dryness of the cover material is improved due to the reduced surface area of the cover material which contacts the wearer""s skin.
The cover material includes a fine denier component having fibers from about 3 dpf to about 5 dpf and a large denier component having fibers or filaments from about 10 dpf to about 100 dpf. The cover material can include multiple discrete or distinct layers or the large denier filaments can be intermixed with the fine denier fibers to produce a single layer multi-denier cover material. The fine denier fibers and the large denier filaments can include the same base material, for example a polypropylene polymer material, or each can include a different base material, such as a polymer blend, to improve the softness and offset the stiffness of the large denier component.
In one embodiment of this invention, the single layer multi-denier cover material can be produced using a spunbond process, wherein the large denier filaments are spun and intermixed with the fine denier fibers. The fine denier fibers and the large denier filaments can be spun from the same spinning plates having an appropriate hole arrangement or the fibers and filaments can be spun from separate spinning plates. The filaments can be bonded to the fibers using suitable bonding methods, such as thermal bonding, through-air bonding, ultrasonic bonding and other suitable bonding methods known to those having ordinary skill in the art.
Alternatively, the cover material having distinct layers of fine denier fibers and the large denier filaments can be produced. A base material layer, for example a 0.5 osy spunbond nonwoven web having fine denier fibers of about 3 dpf to about 5 dpf fibers is formed. Subsequently, a plurality of streams each including a plurality or group of large denier filaments of about 10 dpf to about 100 dpf can be disposed or placed onto a surface of the base material layer. Desirably, but not necessarily, the streams of the large denier filaments are laid in a generally machine or longitudinal direction to produce a plurality of channels. The channels direct fluid to flow in a longitudinal direction rather than a lateral or cross-machine direction to reduce fluid leakage.
The separation or spacing between the streams of the high denier filaments can be controlled to tailor a cover material for specific needs. For example, in an absorbent system having relatively quick absorption, it may be desirable to have a small level of separation between the streams of the large denier filaments. Conversely, in an absorbent system having relatively slow absorption, it may be desirable to have a greater level of separation between the streams of the large denier filaments to increase the void volume in the cover material so a relatively large amount of fluid can be retained until the fluid is absorbed by the underlying absorbent structure without leakage.
With the foregoing in mind, it is a feature and advantage of the invention to provide a material suitable for use as a cover material or bodyside liner for a personal care absorbent article having improved fluid handling characteristics.
It is further a feature and advantage of the invention to provide a cover material or bodyside liner for a personal care absorbent article having a unique topography and texture as well as enhanced visual and tactile properties.
It is further a feature and advantage of the invention to provide a method for producing a material having a fine denier component including fine denier fibers of about 3 dpf to about 5 dpf and a large denier component including large denier fibers of about 10 dpf to about 100 dpf.